Electronic devices are used today in almost all areas of life, especially in industry, in the field of measurement and control technology, in measuring devices, sensors, transmitters, etc.
Electronic devices incorporate electronic components, e.g. microcontrollers, microprocessors or digital signal processors, which serve for performing processes in the devices. Processes include e.g. calculations, comparisons, adjustments, calibrations or compensations.
Electronic devices encompass, for example, measuring devices, which register a physical variable, e.g. a pressure, signal travel time, signal amplitude or a capacitance. The physical variable is converted by means of a transducer unit into an electrical variable, which is then conditioned and evaluated. In such case, as a rule, a multiplicity of different processes occur, which are performed in the electronic device.
There are e.g. fill level measuring devices on the market, which emit a transmission signal, e.g. an ultrasonic signal or a microwave signal, in the direction of a fill substance located in a container, then register its echo signal, and, on the basis of the received echo signal, calculate a current fill level. The calculation requires execution of a multiplicity of different processes, including e.g. temperature compensation of the echo signal, derivation of an echo function presenting amplitude of the echo signal as a function of travel time, identification of a wanted echo attributable to a reflection on a surface of the fill substance, derivation of a travel time of the wanted echo, and determination of the current fill level on the basis of such travel time.
For the individual processes, there are, as a rule, predetermined algorithms available, which are worked through sequentially.
Additionally, further complex calculations can be required, such as e.g. calculation of flow through a ditch, or trough, as a function of measured fill level.
In measurement and control technology, it is, in such case, of special importance to be able to obtain a desired result as rapidly and resource-conservingly as possible. Electronic devices are frequently integrated into large plants and form a part of a large control and regulation system. In such case, as a rule, many different electric devices are distributed over the plant and e.g. connected via a bus connection, such as e.g. Fieldbus, Profibus, or the like, to a superordinated unit, e.g. a process control system or a programmable logic controller. In such case, it is important that each component exhibits short response times, in order that the entire system can react sufficiently rapidly. This is, for example, especially important in industrial manufacturing and/or processing operations. In the case of bus connections, the data transmission satisfies rigidly predetermined standards. In these standards, as a rule, a so-called response time is prescribed. This is the time, which is available to the electronic device following a query. Within this time, the relevant response must be placed on the bus. Typical queries concern, for example, measured values, which are updated in regular intervals. If the response can not be calculated sufficiently rapidly, or be made available, as the case may be, then complicated buffer remedies must be provided. Only in this way is it possible to assure that the device can maintain short response times even during the calculating of the updated measured values. In such case, as a rule, the last-calculated measured value is stored in a memory. Upon queries which enter during the calculating of the new, measured value, the previous measured value stored in the buffer is issued as response. Such buffer solutions are, however, expensive.
In electronic devices, only limited resources are available. As a rule, the available computing power and the available energy are strongly limited.
In order, in spite of this, to achieve short response times in the case of electronic devices, a method is described in DE 697 16 922 T2 for performing a calculation of a function F(X). Thus, in a detailed calculation, the function F(X) is determined, and, following thereon, also its derivative F′(X). In order to assure short response times, the two calculations are regularly interrupted, in order to determine an approximate solution for the calculation, which is then available on very short notice.
The detailed calculation is repeatedly interrupted, in order to calculate an estimate of the result. The estimate is rapidly available, however has a correspondingly lesser accuracy. The time required for the detailed calculation gets longer by the amount of time needed for calculating the approximate solutions.